Fluid Transfer Devices With Fluid Bypass And Ambulatory Infusion Devices Including Same

ABSTRACT

Fluid transfer devices for use in, for example, ambulatory infusion devices and infusions devices including fluid transfer devices.

BACKGROUND

1. Field

The present devices relate generally to pumps, fluid transfer devices,and apparatus including the same.

2. Description of the Related Art

A wide variety of fluid transfer devices, which commonly include a pumpand one or more valves, are configured to transfer relatively smallvolumes of fluid per actuation of the pump. Implantable (or otherwiseambulatory) infusion devices, for example, frequently include a fluidtransfer device that has an electromagnet pump and one or more valves.Examples of conventional electromagnet pumps for ambulatory infusiondevices are disclosed in U.S. Pat. No. 6,796,777 to Falk et al. and U.S.Pat. No. 6,932,584 to Gray. Pipettors are another exemplary area wherepumps and fluid transfer devices that transfer relatively small volumesof fluid per pump actuation are employed.

The present inventor has determined that conventional fluid transferdevices and pumps for small volume applications are susceptible toimprovement. For example, the present inventor has determined thatconventional electromagnet pumps and fluid transfer devices arerelatively complex in that they include a plethora of very smallcomponents, many of which are difficult to produce and assemble, andthat the complexity may reduce reliability. The present inventor hasalso determined that the amount of power consumed by conventionalelectromagnet pumps could be reduced. The present inventor has alsodetermined that the amount of ullage in conventional pumps, which makesit difficult to pump gas bubbles, can be reduced.

Fluid transfer devices in accordance with at least some of the presentinventions include a pump and a valve. The valve, which may be an inletvalve or a one-way outlet valve, includes a valve base, with a sealsurface, and a resilient structure mounted in tension on the valve base.The resilient structure has a valve member movable between a closedstate where the valve member engages the seal surface and an open statewhere at least a portion of the valve member is spaced apart from theseal surface.

Fluid transfer devices in accordance with at least some of the presentinventions include a valve and a pump. The valve, which may be an inletvalve or a one-way outlet valve, includes a seal surface and a resilientmembrane with a least one narrow opening and a valve member associatedwith the narrow opening. The resilient membrane is movable between aclosed state where the valve member engages the seal surface and an openstate where at least a portion of the valve member is spaced apart fromthe seal surface. The pump includes a piston that is biased to a restposition and is movable to a pull-back position. In those instanceswhere the valve is an inlet valve, the piston holds the valve memberagainst the seal surface when in the rest position.

Fluid transfer devices in accordance with at least some of the presentinventions include an external housing member, an internal housingmember defining a piston lumen, an outer surface having a perimeter, anda bypass aperture, a bypass channel in fluid communication with thebypass aperture, a resilient valve member that extends around theinternal housing member and over the bypass aperture outlet, and apiston carried within the piston lumen.

Fluid transfer devices in accordance with at least some of the presentinventions include an external housing tube, an internal housing tubedefining a piston lumen and a bypass aperture, a bypass channel definedby the external housing tube and the internal housing tube in fluidcommunication with the bypass aperture, a valve member associated withthe bypass aperture, and a piston carried within the piston lumen.

Fluid transfer devices in accordance with at least some of the presentinventions include an electromagnet and a piston. The electromagnet hasa coil, a case, and a core having a fluid lumen, and at least a portionof the core is located within the internal volume defined by the case.The piston, which has at least a portion that is magnetic and is locatedwithin the internal volume defined by the case, is movable relative tothe core between a rest position and a pull-back position adjacent tothe core, and is biased to the rest position.

Fluid transfer devices in accordance with at least some of the presentinventions include an inner pump tube defining a piston lumen, an outerpump tube, a piston that does not include a fluid lumen and has at leasta portion thereof mounted within the piston lumen such that a capillaryseal is formed between the piston and the inner pump tube, anelectromagnet including a coil carried outside the outer pump tube and acore having a fluid lumen carried inside the outer pump tube, a bypasschannel defined at least in part by in the inner and outer pump tubes,and a bypass valve.

Fluid transfer devices in accordance with at least some of the presentinventions include a housing defining a piston lumen, a piston stopincluding a fluid lumen, a piston which does not include a fluid lumen.The first end of the piston and the piston lumen together define aninlet chamber, and the second end of the piston and the piston stoptogether define an outlet chamber. The piston is movable between a firstposition where the volume of the inlet chamber is minimized and a secondposition where the piston abuts the piston stop and the prevents flowinto the inlet of the piston stop lumen.

Infusion devices in accordance with at least some of the presentinventions include a reservoir, an infusion device outlet, and a fluidtransfer device as described in the preceding paragraphs of this Summaryoperably connected to the reservoir and the infusion device outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed descriptions of exemplary embodiments will be made withreference to the accompanying drawings.

FIG. 1 is a perspective view of a fluid transfer device in accordancewith one embodiment of a present invention.

FIG. 2 is a section view taken along line 2-2 in FIG. 1 showing thefluid transfer device illustrated in FIG. 1 in a rest state.

FIG. 3 is a section view showing the fluid transfer device illustratedin FIG. 1 in an actuated state.

FIG. 3A is a section view showing a portion of the fluid transfer deviceillustrated in FIG. 1.

FIG. 4 is a perspective view of an inlet tube including a valvestructure in accordance with one embodiment of a present invention.

FIG. 5 is a perspective view of a valve structure in accordance with oneembodiment of a present invention.

FIG. 6 is a plan view of a portion of the valve structure illustrated inFIG. 5.

FIG. 6A is a plan view of a portion of a valve structure in accordancewith one embodiment of a present invention.

FIG. 7 is a section view of the inlet tube and valve structuresillustrated in FIGS. 4-6 showing the valve in a closed state.

FIG. 8 is a section view of the inlet tube and valve structuresillustrated in FIGS. 4-6 showing the valve in an open state.

FIG. 9 is a front view of a pump tube in accordance with one embodimentof a present invention.

FIG. 10 is a section view taken along line 10-10 in FIG. 1.

FIG. 11 is an enlarged view of a portion of FIG. 2.

FIG. 12 is a perspective view of a valve structure in accordance withone embodiment of a present invention.

FIG. 13 is a perspective view of a piston in accordance with oneembodiment of a present invention.

FIG. 13A is an enlarged view of a portion of the fluid transfer deviceillustrated in FIG. 2.

FIG. 14 is a perspective view of an electromagnet core in accordancewith one embodiment of a present invention.

FIG. 15 is a section view take along line 15-15 in FIG. 14.

FIG. 15A is a section view showing the fluid transfer device illustratedin FIG. 1 in a rest state.

FIG. 16 is an enlarged view of a portion of FIG. 2.

FIG. 17 is an enlarged view of a portion of FIG. 2.

FIG. 18 is an enlarged view of a portion of FIG. 3.

FIG. 19 is an enlarged view of a portion of FIG. 3.

FIG. 20 is an enlarged view showing a valve in an open state.

FIG. 21 is a section view of a fluid transfer device in accordance withone embodiment of a present invention in a rest state.

FIG. 22 is a section view showing the fluid transfer device illustratedin FIG. 21 in an actuated state.

FIG. 23 is a section view of a valve structure in a closed state.

FIG. 24 is a section view of a valve structure in an open state.

FIG. 25 is a plan view of an implantable infusion device in accordancewith one embodiment of a present invention.

FIG. 26 is a plan view of the exemplary implantable infusion deviceillustrated in FIG. 25 with the cover removed.

FIG. 27 is a partial section view taken along line 27-27 in FIG. 25.

FIG. 28 is a block diagram of the exemplary implantable infusion deviceillustrated in FIGS. 25-27.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the inventions. This description is not to betaken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions. The presentinventions are also not limited to use in conjunction with the exemplaryimplantable infusion devices described herein and, instead, areapplicable to other implantable or otherwise ambulatory infusion devicesthat currently exist or are yet to be developed, as well as otherapparatus that employ pumps and fluid transfer devices in relatively lowvolume per actuation applications. Examples of such apparatus include,but are not limited to, portable (e.g. battery operated) inflationdevices such as pressure cuffs, hydraulic cutters, and balloon fillers;microfluidic cooling systems for electronics, such as those which coolindividual microprocessor chips; high efficiency micro refrigerationsystems; microfluidic pumps for fuel cells, such as small fuel cells forportable computers, cell phones, and the other electronic devices; andmicrodispensing pumps for pipettors and printers, such as dispensers instereo lithography machines.

One example of a fluid transfer device in accordance with at least oneof the present inventions is generally represented by reference numeral100 in FIGS. 1-3. The exemplary fluid transfer device 100 includes apump 102, an inlet valve 104 (sometimes referred to in the art as a“main check valve”) and a bypass valve 106. Inlet tubes 108 and 110 anda filter 112 are associated with one end of the pump 102, and an outlettube 114 is associated with the other end of the pump. Each of thesecomponents is discussed in greater detail below. Also, the welds thatare discussed below with reference to FIG. 15A are not shown in FIGS.1-3 because they may be replaced by other instrumentalities that performthe same function.

The exemplary pump 102 illustrated in FIGS. 1-3 has an outer pump tube116, an electromagnet 118 that has a portion carried within the outerpump tube and a portion carried on the exterior of the outer pump tube,an inner pump tube 120 that is carried within the outer pump tube, and amagnetic piston 122. In addition to facilitating the assembly of thefluid transfer device 100, the outer pump tube 116 also combines withthe inner pump tube 120 and magnetic piston 122 to defines some of theflow channels within the fluid transfer device. Suitable materials forthe outer pump tube include, but are not limited to, non-magneticmaterials such as titanium, 300 series stainless steels, polysulfone,Kapton, and PEEK. The magnetic piston 122 is biased to the rest positionillustrated in FIG. 2 by a spring 124 or other suitable biasing element.An inlet chamber 126 (FIG. 3), which is sometimes referred to in the artas a “pump chamber,” is defined between the inlet valve 104 and one endof the magnetic piston 122, and an outlet chamber 128 (FIG. 2) isdefined between the other end of the magnetic piston 122 and theelectromagnet core 134 (discussed below). The magnetic piston 122overcomes the biasing force associated with the spring 124, and movesfrom the rest position illustrated in FIG. 2 to the pull-back positionillustrated in FIG. 3, when the electromagnet 118 is energized. Thespring 124 drives the magnetic piston 122 back to the rest position whenthe electromagnet 118 is de-energized. As is discussed in greater detailbelow with reference to FIGS. 16-20, movement of the magnetic piston 122to the pull-back position results in a decrease in pressure in the inletchamber 126. The reduction in pressure within the inlet chamber 126causes the inlet valve 104 to open and fluid to flow into the inletchamber. The inlet valve 104 will close once the pressure within inletchamber 126 is equal to pressure at the inlet tube 108. Movement of themagnetic piston 122 to the pull-back position also drives fluid out ofthe outlet chamber 128. When the magnetic piston 122 moves back to therest position, the pressure within the inlet chamber 126 will increaseand open the bypass valve 106 so that fluid will flow into the flowchannels 130 and 130 a (sometimes referred to a “bypass channels”) thatare located between the inner and outer pump tubes 116 and 120 andextend to the outlet chamber 128. The flow channels 130 and 130 a arediscussed in greater detail below with reference to FIGS. 9-11.

The exemplary electromagnet 118 illustrated in FIGS. 1-3 includes a coil132 and a core 134. The coil 132 is carried within a case 136 that ismounted on the exterior of the outer pump tube 116, while the core 134is carried within the outer pump tube. In addition to forming part ofthe electromagnet 118, the core 134 includes a lumen 138 that centersthe spring 124 and forms part of the fluid flow path and also acts as apiston stop. The core 134 and case 136 may be formed from a magneticmaterial, such as AL29-4 superferritic stainless steel alloy for thecore 134, which contacts fluid, and Hiperco 50 for the case 136, whichdoes not contact fluid. The coil 132, which consists of a wound wire orother conductor, is a hollow structure that extends around the core 134.

The exemplary electromagnet core 134 is discussed in greater detailbelow with reference to FIGS. 13-15. It should be noted here withreference to FIGS. 3 and 3A, however, that the electromagnet core 134has an axial length AL_(core) that is substantially less than the axiallength AL_(case) of the electromagnet case 136, and that one of thelongitudinal ends of the core 134 is adjacent to one of the longitudinalends of case 136. An “axial length” is a length measured along thelongitudinal axis A of the fluid transfer device 100. Depending on theparticular embodiment, the core 134 extends from one longitudinal endLE₁ of the case 136 to a point located about 30% to 70% of the way tothe other longitudinal end LE₂ of the case (about 50% in the illustratedembodiment). Put another way, the case 136 defines an internal volume IVthat has an axial length which is equal to the axial length AL_(case) ofthe case. The core 134 is located within a portion of the longitudinalextent of the internal volume. Also, one end of the core 134 extendsbeyond the longitudinal end LE₁ of the case 136 in the illustratedembodiment. The magnetic piston 122, or at least a portion thereof,occupies the remainder of the length of the internal volume of the case136. Such an arrangement is more efficient that the conventionalarmature design, where the armature pole is located in spaced relationto the electromagnet, which facilitates longer battery life and/oradditional power consuming functionality.

The exemplary electromagnet case 136 illustrated in FIGS. 1-3A includesan inner tube 137, an outer tube 139 and end caps 141. The inner tube137 has magnetic portions 137 a and 137 b and a non-magnetic spacer 137c between the magnetic portions (FIG. 3A). Alternatively, theelectromagnet case may be fabricated in two cylindrical halves bymachining or by metal injection molding. The electromagnet case 136 alsoincludes holes (not shown) to permit the wire leads of the coil 132 tobe connected to an energy source.

Turning to FIGS. 4-8, the exemplary inlet tube 108 is a generallycylindrical structure that includes a main portion 140, an inlet valvebase 142 with a seal surface 143 that has a protrusion 144, and an innerlumen 146 with an outlet end at the inlet chamber 126. The protrusion144 reduces the contact area between the seal surface and the movablevalve member 160 (discussed below) and, therefore, results in greatersealing pressure than that which would be associated with two flatsurfaces. The diameter of the main portion outer surface 148 isessentially equal to the diameter of the inner surface 149 of the outerpump tube 116 and is greater than the diameter of the inlet valve baseouter surface 150. In addition to the inlet valve base 142, the inletvalve 104 includes a resilient cup-shaped structure 152 with acylindrical wall 154 and an end wall 156. The end wall 156 has aplurality of slots 158 that form a movable valve member 160 and aplurality of valve member supports 162 that connect the movable valvemember to the remainder of the end wall 156. In its unstressed state(FIG. 5), the inner diameter of the cylindrical wall 154 of theresilient cup-shaped structure 152 is less than the diameter of theinlet valve base outer surface 150. In some implementations, theunstressed (or “relaxed”) inner diameter of the cylindrical wall 154will be about 50% to 95% of the diameter of the inlet valve base outersurface 150. As a result, the resilient cup-shaped structure 152 must bestretched when it is positioned over the inlet valve base 142 which, inturn, pretensions the cup-shaped structure. The pretension pulls the endwall 156, including the movable valve member 160, against the sealsurface 143 and seal surface protrusion 144. The resilient cup-shapedstructure 152 is held in place by the inlet tube 108 and the inner pumptube 120 after assembly. Adhesive may also be used to secure theresilient cup-shaped structure 152 to the inlet valve base 142 ifdesired. A seal is formed by the seal surface 143, the end wall 156, theinner pump tube 120, the inlet tube 108, the outer pump tube 116, andthe weld W₃ (FIG. 15A) or other joining of the outer pump tube 116 andthe inlet tube 108.

The inner pump tube 120 and magnetic piston 122, which is biased to theposition illustrated in FIG. 2 by spring 124, hold the end wall 156 ofthe resilient cup-shaped structure 152 against the valve base sealsurface 143 in the manner illustrated in FIGS. 7 and 11. The magneticpiston 122 also flattens (or “compresses”) the movable valve member 160against the seal surface protrusion 144. As noted above, movement of themagnetic piston 122 to the pull-back position results in a decrease inpressure within the inlet chamber 126. The reduction in pressure withinthe inlet chamber 126 allows the pressure at the inlet tube 108 toovercome the pretension force on the movable valve member 160. The valvemember 160 will then move away from the seal surface protrusion 144,thereby opening the inlet valve 104 and allowing fluid to flow into theinlet chamber 126 (FIG. 8). More specifically, when some or all of thevalve member 160 moves away from the seal surface protrusion 144, fluidwill be able to flow through some or all of the slots 158. Thepretension force on the valve member 160 will close the inlet valve 104when the pressure within inlet chamber 126 is equal to pressure withinthe inlet tube lumen 146.

With respect to materials, the inlet tube 108, as well as inlet tube 110and outlet tube 114, may be formed from titanium capillary tubing orother suitable tubing. Suitable materials for the resilient cup-shapedstructure 152 include, but are not limited to, elastomers with goodsealing properties, such as silicone rubber, fluoroelastomers,urethanes, and latex rubber. The material that forms the cylindricalwall 154 and end wall 156 may, in some implementations, be a membranethat is about 0.002 inch to about 0.010 inch thick. Wear protection maybe achieved by way of metallization, ceramic ion implantation, foillamination, plastic film lamination, coatings such as plasma depositedsilicate, vacuum deposited parylene, or solution deposited LSR Top Coatfrom GE Silicones. Turning to manufacturing, the resilient cup-shapedstructure 152 may be molded or dip formed. The slots 158 may be formedby die cutting, laser cutting, or molding. In those instances wherelaser cutting is employed, the inclusion of a small percentage ofoptically absorptive filler material in the elastomer will easefabrication.

It should be noted that the present fluid transfer devices are notlimited to the illustrated inlet valve 104. The inlet valve 104 issusceptible to a many variations. By way of example, but not limitation,the slots 158 and valve member 160 may have other configurations thatalso provide minimal opening pressure and fast auto-closure afterpressure equalization. For example a spiral slot may be employed. Slots,slits or other narrow openings (i.e. about 0.000 inch to about 0.005inch) may also be configured such that the valve member consists of asingle flap or is divided into quadrants. A coating, such as plasmadeposited silicate, vacuum deposited parylene, or solution deposited LSRTop Coat from GE Silicones, may be applied to the slit surfaces toreduce adhesion. In other implementations, a protrusion may be providedon valve member instead of the sealing surface 143. For example, theresilient cup-shaped structure 152 a illustrated in FIG. 6A is identicalto the cup-shaped structure 152 but for the protrusion 144 a on thevalve member 160 a. In other implementations, a protrusion may beomitted. Other types of inlet valves may be employed in other fluidtransfer devices in accordance with at least some of the presentinventions. Such alternative inlet valves include, but are not limitedto, each of the inlet valves discloses in U.S. Patent Pub. No.2008/0234638, which is incorporated herein by reference.

Turning to FIGS. 9-12, the exemplary inner pump tube 120 includes agenerally cylindrical main body 164 with an internal lumen 166 for themagnetic piston 122. The inner pump tube 120 is also part of the bypassvalve 106 and the flow channel 130. With respect to the bypass valve106, the inner pump tube 120 includes an annular indentation 168 thatdefines a seal surface 170, a bypass channel 172, and a bypass aperture174. A resilient annular valve member 176 is positioned within theannular indentation 168 over the bypass aperture 174. When the magnetpiston moves from the pull-back position (FIG. 3) to the rest position(FIG. 11), fluid within the inlet chamber 126 (FIG. 3) will be driventhrough the bypass channel 172 and bypass aperture 174 and will stretchthe resilient annular valve member 176 away from the seal surface 170,thereby opening the bypass valve 106 so that fluid will enter the flowchannel 130, as is discussed in greater detail below with reference toFIG. 20. The unstressed inner diameter of the resilient annular valvemember 176 in the illustrated embodiment is only slightly less than thediameter of the seal surface 170, in order to insure that the openingpressure of the bypass valve 106 is minimized.

Although the shapes of the annular indentation 168 and annular valvemember 176 in the illustrated embodiment are such that the interfacebetween the seal surface 170 and annular valve member is flat whenviewed in cross-section (FIG. 11), the shape of the annular indentationand/or annular valve member may be adjusted as desired. By way ofexample, but not limitation, the interface between the seal surface 170and annular valve member 176 may be curved. This may be accomplished by,for example, configuring the annular indentation 168 such that the sealsurface 170 curves inwardly toward the internal lumen 166 andconfiguring the annular valve member 176 such that it has a toroidshape. Alternatively, or in addition, a protrusion similar to protrusion144 may be added to the seal surface 170 around the bypass aperture 174.

It should be noted here that there are a variety of advantagesassociated with the present inlet and bypass valves 104 and 106. Forexample, each valve consists of a single machined part (i.e. the inletvalve base 142 portion of the inlet tube 108 and a portion of the pumptube 120) and a single molded part (i.e. the resilient cup-shapedstructure 152 and the resilient annular valve member 176). The presenttwo-part designs include fewer parts, and are easier to assemble, ascompared to conventional inlet and bypass valves. The configurations ofthe present inlet and bypass valves 104 and 106 also reduce the ullageassociated with the inlet chamber 126, as compared to conventional inletand bypass valves. Ullage associated with an inlet chamber isproblematic because, if air enters the ullage, movement of the piston tothe pull-back position (FIGS. 3 and 8) may not result in a sufficientdecrease in pressure within the pump chamber to open the inlet valveand/or movement back to the rest position (FIGS. 2 and 11) may notresult in a sufficient increase in pressure within the pump chamber toopen the bypass valve. In the illustrated embodiment, the ullageassociated with the inlet chamber 126 is merely the combined volume ofthe slots 158 (FIG. 6) and the bypass channel 172 and bypass aperture174 (FIG. 11). The reduction in ullage increases the expansion ratioduring piston pull-back, increase the compression ratio during pistonreturn, and improves bubble handling, as compared to conventional inletand bypass valves. The ullage of the illustrated embodiment may beminimized by maximizing the depth of the annular indentation 168,thereby minimizing the volume of the bypass aperture 174, to the extentpracticable.

The flow channel 130 (FIGS. 2, 10 and 11), which leads from the bypassvalve 106 to the outlet chamber 128, may be located between the innersurface 149 of the outer pump tube 116 and the outer surface of theinner pump tube 120. In the illustrated embodiment, the flow channel 130is defined by a portion to the generally cylindrical main body that,when measured in a direction perpendicular to the longitudinal axis, issmaller than the diameter of the inner surface 149. To that end, theouter surface of the generally cylindrical main body 164 includes agenerally planar surface 178 that extends from one longitudinal end ofthe main body to the other and is aligned with the bypass aperture 174.Flow channels may be formed in other ways. By way of example, but notlimitation, a channel may be formed by a groove in the outer surface ofthe generally cylindrical main body 164. In either case, the flow (or“bypass”) channel 130 in the present pump 102 is simply a clearancespace between to existing parts of the pump (i.e. the inner and outerpump tubes 120 and 116), which results in smaller, lower profile, andless costly device than conventional pumps that include a separate tubeor hole for the bypass channel, such as that shown in aforementionedU.S. Pat. No. 6,796,777 to Falk et al.

In the illustrated embodiment, a second flow channel 130 a is defined bya second generally planar surface 178 a that extends from onelongitudinal end of the main body 164 to the other. The flow channels130 and 130 a are diametrically opposed, i.e. flow channel 130 acircumferentially offset from flow channel 130 by 180 degrees. Thesecond flow channel provides a flow path for fluid that may travelaround the annular indentation 168 along the outer surface of theresilient annular valve member 176.

The exemplary inner pump tube 120 also include channels 180 (only oneshown) on the longitudinal end of the generally cylindrical main body164 opposite the annular indentation 168. The channels 180 extend fromthe internal lumen 166 to the planar surfaces 178. The channels 180provide a path for fluid that may be trapped between the end of theinner pump tube 120 and the piston second cylindrical portion 184(discussed below with reference to FIGS. 13 and 13A) in order to reducethe amount of force required to move the magnetic piston 122 from therest position.

Suitable materials for the exemplary inner pump tube 120 arenon-magnetic and include, but are not limited to, titanium (e.g.titanium capillary tubing), ceramic and plastics. Ceramics and plasticsare also advantageous in that they result in lower eddy current energylosses. The internal lumen 166 may be treated using suitable depositionand/or implantation processes to improve medication compatibility and/orwear resistance. Suitable materials for the resilient annular valvemember 176 include, but are not limited to, elastomers with good sealingproperties such as low durometer silicone rubber, fluoroelastomers,urethanes, and latex rubber. The elastomers may be coated or treated toreduce adhesion to the seal surface 170.

As illustrated in FIG. 13, the exemplary magnetic piston 122 is a solid,lumen-free structure that includes a first, second and third cylindricalportions 182, 184 and 186. The diameter of the outer surface 187 of thefirst cylindrical portion 182, which is located within the internallumen 166 of the inner pump tube 120, is less than the diameter of theouter surface 188 of the second cylindrical portion 184. The diameter ofouter surface 188 is less than the diameter of the inner surface 149 ofthe outer pump tube 116 and a flow channel 190 (FIG. 13A) is definedtherebetween. In the illustrated embodiment, the diameter of the outersurface 188 is approximately equal to the distance between the planarsurfaces 178 and 178 a (FIG. 10). The flow (or “bypass”) channel 190 isannularly shaped and is connected to flow channels 130 and 130 a. Thediameter of the outer surface 192 of the third cylindrical portion 186is less than the diameter of the outer surface 188.

The clearance between the internal lumen 166 and the first cylindricalportion outer surface 187 is relatively small (about 0.0005 inch in theillustrated embodiment). The small clearance creates a narrow capillarychannel that holds liquid and isolates, with respect to the internallumen 166, the inlet chamber 126 (FIGS. 3 and 8) the outlet chamber 128(FIGS. 2 and 13A). The liquid also forms a viscous piston ring that, dueto the relatively long internal lumen 166/piston 122 interface and thesmall circumference of the ring, increases backflow resistance.Self-priming of the exemplary pump may be obtained through the selectionof the length of the internal lumen 166/piston 122 interface, the strokelength, and the aforementioned clearance.

Suitable materials for the magnetic piston 122 include, but are notlimited to, AL29-4 superferritic stainless steel alloy and similarmagnetic materials. The materials may, or may not, be pre-magnetizedinto a permanent magnet. Some or all of the magnetic piston 122 may betreated with a ceramic ion implantation process, the application ofdiamond-like coating, parylene deposition, or a variety of otherprocesses to obtain improved medication compatibility, greater wearresistance, and improved hydrophilicity.

It should also be noted here that, in other implementations, themagnetic piston 122 may be reconfigured and, where appropriate, theinner pump tube 120 may be modified to accommodate the reconfiguredmagnetic piston. By way of example, but not limitation, the magneticpiston in an otherwise identical pump may be configured as a solidcylinder that does not vary in diameter and is the same length as thepiston 122, and the inner pump tube 120 may be correspondinglylengthened such that it abuts the electromagnet core 134. Also, in theillustrated embodiment, the entire piston 122 (but for any surfacecoatings) is formed from magnetic material. In other embodiments, one ormore portions of the piston may be formed by non-magnetic material. Forexample, the first cylindrical portion 182 may be formed from anon-magnetic material while the second and third cylindrical portions184 and 186 are formed from magnetic material. It should also be notedthat, in some fluid transfer devices that employ the exemplary inletvalve 104 and/or bypass valve 106, but not pump 102, a non-magneticpiston may be employed.

Referring to FIGS. 13A-15A, in addition to forming part of theelectromagnet 118, the core 134 includes a lumen 138 that holds andcenters the spring 124 (FIG. 13A), forms part of the fluid flow path,and acts as a piston stop. The exemplary electromagnet core 134 includesa cylindrical main body 194 with a cup-shaped indentation 196 that isenclosed by an annular wall 198 and defines the outlet chamber 128. Thelumen 138 extends from the indentation 196 to a spring abutment 200,where the diameter of the lumen decreases. The outer diameter of thecylindrical main body 194 is essentially equal to the diameter of theinner surface 149 of the outer pump tube 116, and the diameter of theouter surface 192 of the third piston portion 186 is less than the innerdiameter of the wall 198. As such, fluid from the annular flow channel190 will flow past the third piston portion 186 and into the outletchamber 128 when the magnetic piston 122 returns to the rest position(FIG. 13A). Fluid within the outlet chamber 128 is driven into the lumen138 when the piston moves to the pull-back position (FIG. 3), as isdiscussed in greater detail below with reference to FIGS. 16-20.

Turning to FIG. 13A, a portion of the magnetic piston 122, the spring124, and a portion of the electromagnet core 134 form an outlet valve201 (FIG. 13A) that prevents flow in excessive flow situations (e.g.reservoir overfill or a vacuum applied to the outlet during a diagnosticprocedure) and/or where the magnetic piston is being held in thepull-back position for prolonged periods (e.g. the patient and pump aresubjected to a strong magnetic field, such as that associated with anMRI). In either case, the outlet valve 201 is closed when the magneticpiston 122 is in the pull-back position against the electromagnet core134, thereby preventing flow though the lumen 138. More specifically,flow through the pump 102 is prevented when the magnetic piston endsurface 204 engages the electromagnet core seal surface 197. In theillustrated implementation, the electromagnet core seal surface 197 hasa gasket 202 which improves the seal associated with the outlet valve201 and quiets the operation of the pump 102. In other implementations,the piston end surface 204 may include a gasket, or the gasket maysimply omitted. The gasket 202 may be formed as a discrete element andsecured to the associated surface, or may be applied to the associatedsurface as a coating. Suitable gasket materials include, but are notlimited to, elastomers with good sealing properties such as lowdurometer silicone rubber, fluoroelastomers, urethanes, and latexrubber. Additionally, in some implementations, a small leakage path canbe added to the gasket 202 to prevent long term lock-up of the outletvalve 201.

With respect to excessive flow, the exemplary outlet valve 201 preventsflow through the pump 102 when there is a relatively high pressuredifferential across the pump. The flow rate through the pump 102corresponds to the pressure differential across the pump and, when theflow rate reaches a predetermined threshold, the associated force on themagnetic piston 122 will overcome the biasing force of the spring 124and the piston will move to the pull-back position, thereby closing theoutlet valve 201 and preventing additional flow. The threshold pressureis a function of the cross-sectional area of the flow channel 190 aroundthe second cylindrical piston portion 184 and the spring constant of thespring 124. Because the deflection of the spring 124 is quite smallrelative to its length, pressure sufficient to force open the inletvalve 104 and, possibly, the bypass valve 106, will also close theoutlet valve 201. Fluid flowing through the narrow gap between the longinternal lumen 166 and the piston 122, as well as the narrow flowchannel 190 between the piston surface 188 and the inner surface of theouter pump tube 149, produces drag force that acts on the piston andaids in the closing of the outlet valve 201. A pressure differentialsufficient to counteract the force of spring 124 will also maintain theoutlet valve 201 in the closed state.

Similarly, when an external magnetic field moves the magnetic piston tothe pull-back position, the outlet valve 201 will prevent flow throughthe pump 102. As such, regardless of the reservoir pressure or any othercircumstance that results in pressure differential across the pump 102,placement of the pump in a strong magnetic field will not result inuncontrolled flow.

In addition to the above described safety aspects, the outlet valve 201is also advantageous in that it takes the place of separate safetyvalves that are often included in infusion devices, either upstream ordownstream of the infusion device pump. As such, the outlet valve 201simplifies and reduces the cost of the associated infusion device byincorporating the safety valve functionality within the pump through theuse of structures that are already part of the pump.

The exemplary filter 112 illustrated in FIGS. 2 and 3, which is heldbetween the inlet tubes 108 and 110 by a connector tube 206, preventsparticulate contamination from reaching the interface between the innerpump tube 120 and the magnetic piston 122 and interfering with pistonmovement. Put another way, although the bypass valve 106 and flowchannels 130, 130 a and 190 allow almost all of the fluid and anyparticulates therein to avoid the sensitive interface between the innerpump tube 120 and the piston 122, the filter provides additionalprotection. The filter 112 also prevents bubbles from entering the pump102.

The exemplary fluid transfer device 100 may be assembled in thefollowing manner. First, various sub-assemblies may be separatelyassembled, e.g. the resilient cup-shaped structure 152 may be stretchedover the inlet valve base 142 on the inlet tube 108, the resilientannular valve member 176 may be stretched and positioned within theannular indentation 168 on the inner pump tube 120, the magnetic piston122 may be inserted into the inner pump tube, the spring 124 may beinserted into electromagnet core lumen 138, the inlet tube 110 may bewelded by weld W₁ (or swaged) to the connector tube 206 and the filter112 positioned therein, and outlet tube 114 may be inserted into theouter pump tube 116 and welded by weld W₂ (or swaged) in place (i.e. thelocation illustrated in FIG. 15A). The end of the outer pump tube 116opposite the outlet tube 114 is referred to in this paragraph as the“open end.” Next, the electromagnet core 134 (with spring 124 and gasket202) may be inserted into the open end of the outer pump tube 116,followed by the sub-assembly consisting of the inner pump tube 120,magnetic piston 122, and resilient annular valve member 176. The innerpump tube 120 and the core 134 are secured to the outer pump tube 116,thereby fixing the distance between the magnetic piston 122 and thecore. This may be accomplished by, for example, press-fitting the innerpump tube 120 and the core 134 into the outer pump tube 116, swaging,spot welding from the outside through the outer pump tube, or adhesivebonding. The sub-assembly consisting of the inlet tube 108 and resilientcup-shaped structure 152 may be inserted into the open end of the outerpump tube 116. The inlet tube 108 may then be secured to the outer pumptube 116 by, for example, a laser weld W₃ (or swaging). The sub-assemblyconsisting of the inlet tube 110, filter 112 and connector tube 206 maythen be secured to the inlet tube 108 by weld W₄ (or swaging) theconnector tube to the inlet tube. The electromagnet 118 may then bepositioned over the outer pump tube 116 and secured in place with, forexample, adhesive.

There are a variety of advantages associated with a fluid transferdevice that may be assembled in this manner. By way of example, by notlimitation, only four welds are required to assemble the fluid transferdevice 100, while approximately fifteen welds may be required toassembly a conventional fluid transfer device, such as that illustratedin U.S. Pat. No. 6,796,777 to Falk et al., with a pump, an inlet valveand a bypass valve. Additionally, none of the welds associated with thefluid transfer device 100 are located in an area where weld debris couldget into flow path and cause the pump to fail, which is not the case inmany other fluid transfer devices, including that illustrated in U.S.Pat. No. 6,796,777 to Falk et al.

In an alternative assembly method, which is particularly applicable tothose fluid transfer device implementations where the magnetic pistondoes not vary in diameter and the inner pump tube 120 abuts theelectromagnet core 134, the sub-assembly consisting of the inlet tube108 and resilient cup-shaped structure 152 (with or without theadditional sub-assembly consisting of the inlet tube 110, filter 112 andconnector tube 206) may be secured to the outer pump tube 116 first. Theend of the outer pump tube 116 opposite the inlet tube 108 is referredto in this paragraph as the “open end.” The other sub-assemblies maythen be inserted into the open end of the outer pump tube 116 in thereverse order of the assembly method described in the precedingparagraph. Next, a spring that will be located between the electromagnetcore 134 and the outlet tube 114 (not shown) may be inserted into theopen end of the outer pump tube 116. This spring may be a coil spring, awave spring, a ball-seal spring or a Bellville spring.

Turning to operation, the exemplary fluid transfer device 100 is shownin the rest state in FIGS. 16 and 17. The magnetic piston 122 is in therest position, the electromagnet 118 is not energized, and the inlet andbypass valves 104 and 106 are both closed. Fluid is located within theflow channels 130, 130 a and 190, as well as within the outlet chamber128. Under normal operating conditions, there will be no flow throughthe fluid transfer device 100 when the fluid transfer device is in therest state. Although pressure at the inlet tube 108 in excess of thatrequired to open the inlet valve 104 when the fluid transfer device 100is in the rest state may be encountered (e.g. as a result of reservoiroverpressure in an infusion device), the outlet valve 201 (FIG. 13A),which is formed by a portion of the magnetic piston 122, the spring 124,and a portion of the electromagnet core 134, will close. Theopening/closing pressure differential may be made relatively smallthrough the selection of the parameters of spring 124, the diameter ofthe second cylindrical piston portion 184, the diameter of the outertube inner lumen 149, and the length of the internal lumen 166 and flowchannel 190. This aspect of the exemplary fluid transfer device 100 mayalso eliminate the need for a separate pressure regulator, which isfrequently employed in implantable infusion devices to preventunintended infusion to the patient.

The exemplary fluid transfer device 100 is actuated by connecting thecoil 132 in the electromagnet 118 to an energy source (e.g. one or morecapacitors that are being fired). The resulting magnetic field isdirected through the core 134 and into, as well as through, the magneticpiston 122. The magnetic piston 122 is attracted to the core 134 by themagnetic field. The intensity of the magnetic field grows as currentcontinues to flow through the coil 132. When the intensity reaches alevel sufficient to overcome the biasing force of the spring 124, themagnetic piston 122 will be pulled rapidly toward the core 134, and willcompress the spring, until the magnetic piston portion 186 reaches thepull-back position and strikes the gasket 202 (FIGS. 18 and 19). Putanother way, in addition to driving fluid from the inlet and outletchambers 126 and 128, the magnetic piston 122 also performs the functionof the armature pole in a conventional electromagnet pump, albeit from adifferent position relative to the electromagnet, and the electromagnetcore 134 also functions as a piston stop.

Movement of the magnetic piston 122 from the rest position illustratedin FIGS. 16 and 17 to the pull-back position illustrated in FIGS. 18 and19 results in a decrease in pressure in the inlet chamber 126. The coil132 will continue to be energized for a brief time (e.g. a fewmilliseconds) in order to hold the magnetic piston 122 in the pull-backposition. The reduction in pressure within the inlet chamber 126 willresult in a pressure differential across the valve member 160 that willovercome the pretension associated with the stretching of the cup-shapedstructure 152 and cause some or all of the valve member to move awayfrom the seal surface protrusion 144, thereby opening the inlet valve104. Fluid from the inlet tube inner lumen 146 will flow into the inletchamber 126. The inlet valve 104 will close, due to the pretension ofthe cup-shaped structure 152, once the pressure within inlet chamber 126is equal to pressure at the inlet tube inner lumen 146. Because the coil132 continues to be energized, the magnetic piston will remain in theposition illustrated in FIGS. 18 and 19 as fluid flows into the inletchamber 126 and the inlet valve 104 closes.

Movement of the magnetic piston 122 from the rest position illustratedin FIGS. 16 and 17 to the pull-back position illustrated in FIGS. 18 and19 also results in fluid exiting the fluid transfer device 100 by way ofthe outlet tube 114 (FIG. 3) and maintains the bypass valve 106 in aclosed state. More specifically, such movement of the magnetic piston122 increases the pressure in the outlet chamber 128 and drives fluidthrough the lumen 138 in the electromagnet core 134. The pressure withinthe flow channels 130, 130 a and 190 also increases, which seals thebypass valve 106 more tightly.

Shortly after the inlet valve 104 closes, the coil 132 will bedisconnected from the energy source and the magnetic field establishedby the electromagnet 118 will decay until it can no longer overcome theforce exerted on the magnetic piston 122 by the spring 124. The magneticpiston 122 will then move back to the position illustrated in FIGS. 16and 17, to more firmly hold the inlet valve 104 closed. The associatedincrease in pressure within the inlet chamber 128 will open the bypassvalve 106 by stretching the portion of the resilient annular valvemember 176 adjacent to the bypass aperture 174 away from the sealsurface 170. Fluid will flow past the annular valve member 176, into theannular indentation 168 and then into the flow channels 130 and 130 a.This fluid will ultimately reach the outlet chamber 128 by way of theflow channel 190.

In the exemplary context of implantable drug delivery devices, andalthough the volume/stroke magnitude may be increased in certainsituations, the fluid transfer devices will typically deliver about 1microliter/stroke or other actuation, but may be more or less (e.g.about 0.25 microliter/actuation or less) depending on the particularfluid transfer device employed.

Although the present fluid transfer devices are not limited to anyparticular size or application, one example of a fluid transfer devicethat may be used in an implantable infusion device (“the exemplaryconfiguration”) may be sized as follows. Referring to FIGS. 4-7, theinlet tube 108 in the exemplary configuration has a main portion 140that is about 0.25 inch in length and about 0.093 inch in diameter, aninlet valve base 142 that is about 0.059 inch in length and about 0.086inch in diameter, a protrusion 144 that extends about 0.001 inch fromthe seal surface 143, and an inner lumen 146 that is about 0.010 inch indiameter. The resilient cup-shaped structure 152 in the exemplaryconfiguration is about 0.063 inch in length has an unstressed diameterthat is about 0.075 inch (i.e. about 50%-95% of the valve base diameter)and is about 0.003 inch thick. The diameter of the movable valve member160 is about 0.016 inch. Turning to FIGS. 9 and 10, the inner pump tube120 in the exemplary configuration is about 0.260 inch in length andabout 0.093 inch in diameter, and has a main body 164 that is about0.236 inch in length, an internal lumen 166 that is about 0.050 inch indiameter, an annular indentation 168 that is about 0.014 inch in lengthand about 0.083 inch in diameter, a bypass aperture 174 that is about0.005 inch in diameter, and planar surfaces 178 that are about 0.026inch wide (measured perpendicular to the longitudinal axis of the innerpump tube) which creates a maximum distance between the planar surfaces178 and the outer pump tube inner surface 149 of about 0.003 inch.Referring to FIGS. 13-15, the magnetic piston 122 in the exemplaryconfiguration has a first cylindrical portion 182 that is about 0.254inch in length and about 0.050 inch in diameter, a second cylindricalportion 184 that is about 0.127 inch in length and about 0.087 inch indiameter, and a third cylindrical portion 186 that is about 0.013 inchin length and about 0.077 inch in diameter. The flow channel 190 isabout 0.003 inch thick. The electromagnet core 134 in the exemplaryconfiguration is about 0.196 inch in length and about 0.093 inch indiameter, and has a cup-shaped indentation 196 that is about 0.013 inchdeep and about 0.083 inch in diameter and a lumen 138 that is about0.026 inch in diameter and about 0.170 inch in length. The surface 197is separated from the piston end surface 204 by about 0.013 inch whenthe pump 102 is in the rest state. The spring 124 has a free length ofabout 0.196 inch and a spring constant of about 1 g/0.001 inch. As such,the spring 124 is compressed about 0.013 inch when the pump is at rest,which creates a 13 g preload. Given that the inner lumen 146 (whichserves as the inlet) is about 0.010 inch in diameter, the forced openingpressure is about 369 psi and, accordingly, the present fluid transferdevice is more tolerant of reservoir overpressure than conventionalfluid transfer devices with larger inlet diameters. It should be notedhere that the relatively small inlet diameter is facilitated by the factthat portions of the inlet valve are not located within the inlet, as isthe case in many conventional fluid transfer devices. Turning to FIGS. 3and 3A, the axial length AL_(case) of the electromagnet case 136 in theexemplary configuration is about 0.380 inch, and the outer pump tube 116is about 0.900 inch in length and has an inner diameter of about 0.093inch.

Another exemplary fluid transfer device in accordance with at least oneof the present inventions is generally represented by reference numeral100 a in FIGS. 21 and 22. The exemplary fluid transfer device 100 a issimilar in many respects to the fluid transfer device 100 and similarelements are represented by similar reference numerals. The descriptionabove of such similar elements is incorporated by reference into thisportion of the present specification. To that end, the fluid transferdevice 100 a includes a pump 102 a, an inlet tube 110 associated withone end of the pump, and an outlet tube 114 associated with the otherend. The exemplary pump 102 a has an outer pump tube 116, anelectromagnet 118 a that has a portion carried within the outer pumptube and a portion carried on the exterior of the outer pump tube, and amagnetic piston 122 a. The magnetic piston 122 a is biased to the restposition illustrated in FIG. 21 by a spring 124. The pump 102 a also hasan inlet chamber 126 (FIG. 22) and an outlet chamber 128 (FIG. 21).Movement of the magnetic piston 122 a to the pull-back positionillustrated in FIG. 22 results in a decrease in pressure in the inletchamber 126, which causes fluid to flow into the inlet chamber. Movementof the magnetic piston 122 a to the pull-back position also drives fluidout of the outlet chamber 128 and through the electromagnet core 134 a(discussed below). When the magnetic piston 122 a moves back to the restposition, the pressure within the inlet chamber 126 will increase andfluid will flow through the capillary interface 208 between the pumptube 116 and the piston 122 a to the outlet chamber 128.

The exemplary electromagnet 118 a includes a coil 132, a core 134 a anda case 136. In addition to forming part of the electromagnet 118 a, thecore 134 a includes a lumen 138 that centers the spring 124, forms partof the fluid flow path, acts as a piston stop, and forms part of aone-way outlet valve 210. To that end, and referring to FIGS. 21-24, theelectromagnet core 134 a has a main portion 212 and a valve base 214with a seal surface 216 that has a protrusion 218. The outer diameter ofthe main portion 212 is essentially equal to the inner diameter of theouter pump tube 116. A pre-tensioned resilient cup-shaped structure 152,with a cylindrical wall 154, an end wall 156, various slots and amovable valve member 160, is configured and carried on the valve base214 in the manner described above with respect to the inlet valve 104.The pretension pulls the end wall 156, including the movable valvemember 160, against the seal surface 216 and seal surface protrusion218, thereby closing the one-way valve 210 and preventing backflow fromthe outlet tube 114 to the pump 102 a (FIG. 23). In those instanceswhere a negative pressure reservoir is employed, the negative pressurewill also pull the movable valve member 160 to the closed position. Theone-way valve 210 is opened (FIG. 24) when movement of the magneticpiston 122 a to the pull-back position drives fluid into, and increasesthe pressure within, the electromagnet core lumen 138. The valve 210will re-close when the pressure within the electromagnet core lumen 138drops.

It should also be noted that a filter (e.g. filter 112) may be mountedon the inlet end of the inlet tube 110 in a manner similar to thatdescribed above with reference to FIGS. 2 and 3. Also, in otherimplementations, a valve such as a poppet valve, a duckbill valve, or acheck valve, may be employed in place of the exemplary one-way outletvalve 210.

It should be noted here that although the various elements of theexemplary fluid transfer devices are annular or circular incross-sectional shape, the present inventions are not so limited.

One example of an infusion device that may employ the exemplary fluidtransfer device 100 (or 100 a) is the implantable infusion devicegenerally represented by reference numeral 300 in FIGS. 25-28. As usedherein, an “infusion device” is a device that includes a permanent orreplaceable reservoir, a fluid transfer device and an outlet, and an“implantable infusion device” is an “infusion device” with a permanentreservoir that is sized, shaped and otherwise constructed (e.g. sealed)such that both the reservoir and outlet can be simultaneously carriedwithin the patient's body. The exemplary infusion device 300 includes ahousing 302 (e.g. a titanium housing) with a bottom portion 304, aninternal wall 306, and a cover 308. An infusible substance (e.g.medication) may be stored in a reservoir 310 that is located within thehousing bottom portion 304. The reservoir 310 may be replenished by wayof a fill port 312 that extends from the reservoir to the cover 308. Ahypodermic needle (not shown), which is configured to be pushed throughthe fill port 312, may be used to replenish the reservoir 310. Fluidflow from the fill port 312 to the reservoir 310 may be controlled by aninlet valve (not shown).

A wide variety of reservoirs may be employed. In the illustratedembodiment, the reservoir 310 is in the form of a titanium bellows thatis positioned within a sealed volume defined by the housing bottomportion 304 and internal wall 306. The remainder of the sealed volume isoccupied by propellant P, which may be used to exert negative pressureon the reservoir 310. Other reservoirs that may be employed in thepresent infusion devices include reservoirs in which propellant exerts apositive pressure. Still other exemplary reservoirs include negativepressure reservoirs that employ a movable wall that is exposed toambient pressure and is configured to exert a force that produces aninterior pressure that is always negative with respect to the ambientpressure.

The exemplary ambulatory infusion device 300 illustrated in FIGS. 25-28also includes the fluid transfer device 100. The inlet of the fluidtransfer device 100 is coupled to the interior of the reservoir 310 by apassageway 317, while the outlet of the fluid transfer device is coupledto an outlet port 318 by a passageway 320. Operation of the fluidtransfer device 100 causes infusible substance to move from thereservoir 310 to the outlet port 318. A catheter 324 may be connected tothe outlet port 318 so that the infusible substance passing through theoutlet port will be delivered to a target body region in spaced relationto the infusion device 300 by way of the outlet 325 at the end of thecatheter.

Energy for the fluid transfer device 100, as well for other aspects ofthe exemplary infusion device 300, is provided by the battery 326illustrated in FIG. 26. In the specific case of the fluid transferdevice 100, the battery 326 is used to charge one or more capacitors328, and is not directly connected to the fluid transfer device itself.The capacitor(s) 328 are connected to the electromagnet coil 132 in thefluid transfer device 100, and disconnected from the battery 326, whenthe electromagnet coil is being energized, and are disconnected from theelectromagnet coil and connected to the battery when the capacitor(s)are being recharged and/or when the fluid transfer device is at rest.The capacitor(s) 328 are carried on a board 330. A communication device332, which is connected to an antenna 334, is carried on the same sideof the board 330 as the capacitor(s) 328. The exemplary communicationdevice 332 is an RF communication device. Other suitable communicationdevices include, but are not limited to, oscillating magnetic fieldcommunication devices, static magnetic field communication devices,optical communication devices, ultrasound communication devices anddirect electrical communication devices.

A controller 336 (FIG. 28), such as a microprocessor, microcontroller orother control circuitry, is carried on the other side of the board 330.The controller controls the operations of the infusion device 300 inaccordance with instructions stored in memory 338 and/or provided by anexternal device by way of the communication device 332. For example, thecontroller 336 may be used to control the fluid transfer device 100 tosupply fluid to the patient in accordance with, for example, a storeddelivery profile or a bolus delivery request (generically referred to asa “delivery instruction”). The controller 336 may also be used tomonitor and/or calculate pressure, to calculate the volume of fluidsupplied with each actuation of the fluid transfer device 100, and toperform other analytical functions.

Referring to FIGS. 25, 26 and 28, the exemplary infusion device 300 isalso provided with a side port 340 that is connected to the passageway320 between the outlet of the fluid transfer device 100 and the outletport 318. The side port 340 facilitates access to an implanted catheter324, typically by way of a hypodermic needle. For example, the side port340 allows clinicians to push fluid into the catheter 324 and/or drawfluid from the catheter for purposes such as checking catheter patency,sampling CSF, injecting contrast dye into the patient and/or catheter,removing medication from the catheter prior to dye injection, injectingadditional medication into the region at the catheter outlet 325, and/orremoving pharmaceuticals or other fluids that are causing an allergic orotherwise undesirable biologic reaction.

The outlet port 318, a portion of the passageway 320, the antenna 334and the side port 340 are carried by a header assembly 342. The headerassembly 342 is a molded, plastic structure that is secured to thehousing 302. The housing 302 includes a small aperture through whichportions of the passageway 320 are connected to one another, and a smallaperture through which the antenna 334 is connected to the board 330.

The exemplary infusion device 300 illustrated in FIGS. 25-28 alsoincludes a pressure sensor 344 that is connected to the passageway 320between the outlet of the fluid transfer device 100 and the outlet port318. As such, the pressure sensor 344 senses the pressure at the outletport 318 which, in the illustrated embodiment, is also the pressurewithin the catheter 324. The pressure sensor 344 is connected to thecontroller 336 and may be used to analyze a variety of aspects of theoperation of the exemplary implantable infusion device 300. An audiblealarm 346, which is located within the housing 302, is also connected tothe controller 336.

Although the inventions disclosed herein have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. It is intended that the scope of the presentinventions extend to all such modifications and/or additions and thatthe scope of the present inventions is limited solely by the claims setforth below.

1-22. (canceled)
 23. An infusion device, comprising: a fluid transferdevice including an external housing member, an internal housing memberlocated within the external housing member and defining a piston lumen,an outer surface having a perimeter, and a bypass aperture having aninlet associated with the piston lumen and an outlet associated with theouter surface, a bypass channel in fluid communication with the bypassaperture outlet, a resilient valve member that extends around theperimeter of the internal housing member outer surface and over thebypass aperture outlet, and a piston carried within the piston lumen; aninfusion device outlet operably connected to the fluid transfer device;and a reservoir operably connected to the fluid transfer device suchthat the fluid transfer device receives fluid from the reservoir.
 24. Aninfusion device as claimed in claim 23, further comprising: a housing;and wherein the fluid transfer device and the reservoir are locatedwithin the housing.
 25. An infusion device as claimed in claim 23,wherein the reservoir comprises a negative pressure reservoir.
 26. Aninfusion device as claimed in claim 23, wherein the internal housingmember outer surface includes an indentation that extends around theperimeter of the internal housing member outer surface; the bypassaperture outlet is located within the indentation; the bypass channelextends to the indentation; and the resilient valve member is locatedwithin the indentation.
 27. An infusion device as claimed in claim 26,wherein the indentation comprises an annular indentation; and theresilient valve member comprises an annular resilient valve member. 28.An infusion device as claimed in claim 26, further comprising: a secondbypass channel that extends to the indentation and is in fluidcommunication with the bypass aperture.
 29. An infusion device asclaimed in claim 23, wherein the resilient valve member comprises anannular resilient valve member.
 30. An infusion device as claimed inclaim 29, wherein the piston defines a longitudinal axis; and theresilient annular valve member defines a rectangle in a cross-sectiontaken parallel to the longitudinal axis.
 31. An infusion device asclaimed in claim 23, wherein the external housing member comprises anexternal tube and the internal housing member comprises an internaltube.
 32. An infusion device as claimed in claim 31, wherein theexternal tube is annular in cross-section and internal tube issubstantially annular in cross-section.
 33. An infusion device asclaimed in claim 23, wherein the external housing member defines aninner surface; and the bypass channel is defined by the external housingmember inner surface and the internal housing member outer surface. 34.An infusion device as claimed in claim 33, wherein the internal housingmember outer surface includes longitudinally extending substantiallyplanar surface; and the bypass channel is defined by the externalhousing member inner surface and the internal housing membersubstantially planar surface.
 35. An infusion device as claimed in claim23, wherein the piston lumen includes an internal bypass channel that isconnected to the bypass aperture inlet.
 36. An infusion device asclaimed in claim 23, wherein the internal housing member defines alongitudinal end; the bypass aperture is located adjacent to theinternal housing member longitudinal end; and the fluid transfer devicefurther comprises an inlet valve located adjacent to the internalhousing member longitudinal end.
 37. An infusion device as claimed inclaim 23, further comprising: a spring that biases the piston to therest position; and an electromagnet that, when actuated, moves thepiston to a pull-back position.
 38. An infusion device, comprising: afluid transfer device including an external housing tube having an innersurface, an internal housing tube located within the external housingtube and defining a piston lumen, an outer surface having a perimeter,and a bypass aperture having an inlet associated with the piston lumenand an outlet associated with the outer surface, a bypass channel,defined by the external housing tube inner surface and the internalhousing tube outer surface, in fluid communication with the bypassaperture outlet, a valve member associated with the bypass apertureoutlet and movable between an open position and a closed position, and apiston carried within the piston lumen; an infusion device outletoperably connected to the fluid transfer device; and a reservoiroperably connected to the fluid transfer device such that the fluidtransfer device receives fluid from the reservoir.
 39. An infusiondevice as claimed in claim 38, further comprising: a housing; andwherein the fluid transfer device and the reservoir are located withinthe housing.
 40. An infusion device as claimed in claim 38, wherein thereservoir comprises a negative pressure reservoir.
 41. An infusiondevice as claimed in claim 38, wherein the internal housing tube outersurface includes longitudinally extending substantially planar surface;and the bypass channel is defined by the external housing tube innersurface and the internal housing member substantially planar surface.42. An infusion device as claimed in claim 38, wherein the piston lumenincludes an internal bypass channel that is connected to the bypassaperture inlet.
 43. An infusion device as claimed in claim 38, whereinthe valve member comprises a resilient valve member that extends aroundthe perimeter of the internal housing tube outer surface and over thebypass aperture outlet.
 44. An infusion device as claimed in claim 43,wherein the internal housing tube outer surface includes an indentationthat extends around the perimeter of the outer surface; the bypassaperture outlet is located within the indentation; the bypass channelextends to the indentation; and the resilient valve member is locatedwithin the indentation.
 45. An infusion device as claimed in claim 44,further comprising: a second bypass channel that extends to theindentation.
 46. An infusion device as claimed in claim 38, wherein theexternal housing tube is annular in cross-section and internal housingtube is substantially annular in cross-section.
 47. An infusion deviceas claimed in claim 38, wherein the internal housing tube defines alongitudinal end; the bypass aperture is located adjacent to theinternal housing tube longitudinal end; and the fluid transfer devicefurther comprises an inlet valve located adjacent to the internalhousing tube longitudinal end.
 48. An infusion device as claimed inclaim 38, further comprising: a spring that biases the piston to a restposition; and an electromagnet that, when actuated, moves the piston toa pull-back position.